Field of the Invention
The present invention relates to a sealing device, and more particularly to a sealing which is provided with a seal lip and a dust lip. The sealing device according to the present invention is used, for example, as a hub bearing seal for a vehicle such as a motor vehicle, or a bearing seal for a construction equipment.
Description of the Conventional Art
As the sealing device used as the hub bearing seal for the vehicle such as to the motor vehicle, there has been conventionally known a sealing device provided with a seal lip 71 which prevents a foreign material in a machine external side A from entering into a machine internal side B, and a dust lip 72 which makes the foreign material hard to reach the seal lip 71, as shown in FIG. 4 (refer to Japanese Unexamined Patent Publication No. 2010-71323 [FIG. 5]).
Further, in the hub bearing seal, a rubber material (a conductive rubber material) blended with a conductive carbon at a predetermined amount has been preferably used in recent years as a static electricity removal countermeasure (a radio noise countermeasure) (refer to Japanese Unexamined Patent Publication No. 2012-97213).
However, it has been known that the rubber material blended with the conductive carbon tends to swell and deform due to immersion of muddy water or salt water, in comparison with the rubber material which is not blended with the conductive carbon.
Accordingly, in the case that all the seal lip 71 and the dust lip 72 are integrally formed by the rubber material blended with the conductive carbon in the sealing device in FIG. 4, the dust lip 72 which is always exposed to an external environment is particularly affected greatly. As a result, there is a problem that a sealing property is deteriorated (there is a risk that the dust lip 72 is swollen and deformed, and the sealing property is deteriorated).